Vortex-type filters are well known and used extensively for filtering fluids, including both liquids and gases. These filters are advantageous because they provide high separation efficiency with minimal pumping losses. Vortex-type filters can be used in a variety of applications, such as separating debris from fluids, separating heavier fluids from lighter fluids, separating particulates from gases, or separating liquid fluids from gas fluids.
A vortex-type filter essentially comprises a vortex generating inlet passage, and a cooperating outlet passage. Both passages may be cylindrical or somewhat conical, and are axially aligned to one another. The entrance of the outlet passage is smaller than the exit of the inlet passage, and is located proximate to the exit of the inlet passage. The passages extend within a filtration chamber that is separated from the entrance of the inlet passage and the exit of the outlet passage. From this filtration chamber, the separated material is drawn by an external source though an aspiration port, or a scavenge port. Such filters are typically packaged within a housing, either individually or in groups, to form a filter assembly that can be used to filter fluids in machinery or power equipment.
In operation, unfiltered fluid enters the inlet passage, where a vortex motion is imparted in the fluid flow. The heaver material in the flow, be it fluid or debris, is thrown radially outward toward the inlet passage walls by the centrifugal force of the vortex motion. Thus, the flow is separated into a lighter portion at the center of the inlet passage, and a heavier portion near the wall of the inlet passage. As the fluid exits the inlet passage, the heaver “separated” portion flows past the entrance of smaller outlet passage and into the filtration chamber, while the lighter “filtered” portion enters and flows through the outlet passage.
In an application such as a work vehicle, filter assemblies having many vortex-type filters are commonly used to “pre-filter” debris from air entering the engine air filter. An example of such an application is an agricultural harvester, where the operating environment may be filled with high levels of dust and plant material being generated from the harvesting machinery. In this example, air is drawn into the inlet passages by the suction of the engine. The heavier dust and plant materials are separated-out and flow into the filtration chamber of the filter assembly, while clean air flows through the outlet passages and on towards the engine. The separated material is then drawn from the filtration chamber of the filter assembly, through the scavenge port, and into exhaust flow of the engine.
With the scavenging method described, the filtration chamber of the filter assembly is continually self-cleaning. As such, the typical vortex-type filter assembly is a sealed unit and does not allow for manual cleaning. Thus, when the scavenge method becomes ineffective and the filtration chamber becomes plugged with separated material, or when the passages themselves become plugged with material, the filter assembly must be replaced. Normally, filter assembly replacement is required infrequently.
However, under certain operating conditions with an agricultural harvester, particularly when harvesting safflower, both the passages and filtration chamber are highly prone to plugging with plant material. Additionally, under certain operating conditions where the air and/or debris are high in moisture, the filtration chamber is highly prone to become caked with moist separated material, which can harden into a brick under heating by the engine. Filter assembly replacement may be frequently required under these and similar conditions. The high cost and amount of downtime attributed to frequent replacement of the filter assembly is very undesirable.